1. Field of the Invention
The present invention relates to an image forming apparatus including a printing device and a scanning device.
2. Description of the Related Art
There is a need to separately arrange a printing device and a scanning device included in an image forming apparatus, such as a copy machine, for improvement of usability. For example, every user including a healthy person and a person in a wheel chair wants to place an image forming apparatus at an accessible height to operate the image forming apparatus in an easy manner. Because accessible heights to an image forming apparatus depend on users, the image forming apparatus can be more user friendly if a printing device and a scanning device can be easily separated depending on needs. Especially, in a case of large-sized copy machines capable of handling originals of larger than A3 size, separate arrangement of a printing device and a scanning device much enhances operability.
However, a conventional copy machine is designed based on assumption that a printing device and a scanning device are integrally arranged while the copy machine is in use. Therefore, an electrical configuration or a mechanical configuration of the conventional copy machine is not preferable for separating the printing device and the scanning device. In some conventional copy machines, the printing device and the scanning device are simply connected to each other via a harness. For example, Japanese Patent Application Laid-open No. H09-321925 discloses such a conventional copy machine.
Harnesses are connected between the scanning device and the printing device to transmit signals from each of sensors included in the scanning device to the printing device. Generally, three harnesses, i.e., a power-supply harness, a ground (GND) harness, and a signal harness, need to be arranged for each of the sensors. The harnesses are put together as a bundle and covered with a shield. Therefore, if the number of harnesses arranged for the sensors increases, the thickness of the bundle of the harnesses also increases, making it difficult to arrange the bundle of the harnesses in a desired place.
In a case of copy machines capable of handling originals of A3 or smaller size, an original-size detecting sensor included in a scanning device generally performs scanning operation on the original that is placed on an exposure glass without conveying the original. In such a copy machine, the size of the original is detected in two dimensions, i.e., a width and a length of the original. The size of the original is detected by a matrix that is defined based on positions of original-size detecting sensors. With this configuration, multiple sizes can be detected by using the small number of original-size detecting sensors.
However, in a case of large-sized copy machines capable of handling originals of larger than A3 size, a size of an original to be scanned can be various. To detect the size of an original, a width of the original is first detected when the original is placed on a platen. Afterward, a length of the original is detected based on a time from when the original is inserted from a first position to when the original is discharged from a second position. With such a configuration, to detect the width of the original placed on the platen, sensors need to be arranged in a line in accordance with the width of an original to be scanned. If ten sensors are arranged for detection of the width, as much as 30 harnesses are necessary for the ten sensors, making a bundle of the harnesses thick. Thus, it is difficult to arrange the thick bundle of the harnesses.